INTRODUCTION: Shoulder dystocia is the strongest risk factor for brachial plexus birth palsy (BPBP). Fractures of the clavicle or humerus are known to occur in the setting of shoulder dystocia and are indicators of birth trauma. It remains unknown whether the presence of a clavicle or humerus fracture in the setting of shoulder dystocia is associated with an increased or decreased risk of BPBP. The purpose of this study was to use the Kids' Inpatient Database (KID) to determine if a clavicle or humerus fracture in the setting of shoulder dystocia is associated with an increased or decreased risk of BPBP.

MATERIALS & METHODS: The 1997-2012 KID was analyzed for this study. ICD-9 codes were used to identify newborns diagnosed with shoulder dystocia and BPBP as well as a concurrent fracture of the clavicle or humerus. Newborns with shoulder dystocia were stratified into three subgroups: dystocia without a humerus or clavicle fracture, dystocia with a clavicle fracture, and dystocia with a humerus fracture. Multivariate logistic regression was used to quantify the risk for BPBP.

RESULTS: The dataset included 5,564,628 sample births extrapolated to 23,385,597 population births. The prevalence of shoulder dystocia was 0.23% among all births and 18.78% in those with BPBP. The prevalence of a clavicle or humerus fracture was 0.26% among all births, 5.85% among births with shoulder dystocia, and 8.05% among births with BPBP. Births with shoulder dystocia and a clavicle fracture experienced BPBP at a rate comparable to births with shoulder dystocia and no fracture (9.82% vs. 11.77%). Shoulder dystocia without a concurrent fracture was an independent risk factor for BPBP (OR 112.1, 95%CI 103.5 - 121.4). The presence of a clavicle fracture (OR 126.7 vs. 112.1, p=0.262) or humerus fracture (OR 143.2 vs. 112.1, p=0.617) in the setting of shoulder dystocia was not statistically associated with an increased risk of BPBP. A post-hoc power analysis indicated >99% power to find a 10% difference in odds ratios between subgroups.

CONCLUSION: Among newborns with shoulder dystocia, clavicle or humerus fractures are not associated with a decreased or increased risk of BPBP. Although a clavicle or humerus fracture characterizes a more difficult or forceful delivery, such fractures may also dissipate forces otherwise transmitted to the brachial plexus. As the search for modifiable risk factors for BPBP continues, further studies are needed to determine whether intentional clavicle fracture at the time of birth may reduce the risk of BPBP.